Hexagonal Semiconductor Package Structure

ABSTRACT

Coil structures and methods of forming are provided. The coil structure includes a substrate. A plurality of coils is disposed over the substrate, each coil comprising a conductive element that forms a continuous spiral having a hexagonal shape in a plan view of the coil structure. The plurality of coils is arranged in a honeycomb pattern, and each conductive element is electrically connected to an external electrical circuit.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional and claims the benefit of U.S. patentapplication Ser. No. 15/232,443, filed on Aug. 9, 2016, entitled“Hexagonal Semiconductor Package Structure,” which application is herebyincorporated herein by reference.

BACKGROUND

Wireless charging has become an increasingly popular chargingtechnology. Wireless charging is sometimes known as inductive charging,which uses an electromagnetic field to transfer power between a powertransmitter and a power receiver. The power is sent through inductivecoupling to an electrical device, which can then use that power tocharge batteries or run the device. Induction chargers use a firstinduction coil to create an alternating electromagnetic field from thetransmitter and a second induction coil to receive the power from theelectromagnetic field. The second induction coil converts the power backinto electric current, which is then used to charge a battery ordirectly drive electrical devices. The two induction coils, whenproximal to each other, form an electrical transformer.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A and 1B are plan views of a coil structure in accordance withsome embodiments.

FIG. 2 is a schematic of a wireless charging circuit in accordance withsome embodiments.

FIGS. 3 and 4 are cross section views of a coil structure in accordancewith some embodiments.

FIGS. 5, 6A and 6B, 7A and 7B, 8A and 8B, 9A and 9B, 10A and 10B, 11Aand 11B, 12A and 12B, and 13A and 13B, are cross sectional diagrams of acoil in intermediate stages of forming a coil structure in accordancewith some embodiments.

FIG. 14 is a cross section diagram of a coil structure in accordancewith some embodiments.

FIG. 15 are plan views of a coil structures in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Coil structures and the methods of forming the same are provided inaccordance with various exemplary embodiments. The intermediate stagesof forming the coil structures are illustrated in accordance with someembodiments. Some variations of some embodiments are discussed.Throughout the various views and illustrative embodiments, likereference numbers are used to designate like elements.

FIGS. 1A and 1B illustrate planar views of coil structure 100, whichcomprises a plurality of coils 104. As shown in FIG. 1B, a wafer 102comprises a plurality of coils 104 on a top surface of wafer 102. Asshown in FIG. 1A, each coil 104 comprises a conductive element 106 thatis arranged in continuous spiral coil. The conductive element 106 isconnected to an external electrical circuit at a first end by electricalconnector 112 and a second end by electrical connector 114. Theconductive element 106 may define the shape of each coil 104. In someembodiments, as shown in FIGS. 1A and 1B, each coil 104 may have ahexagonal shape. In some embodiments, as shown in FIG. 1A, the pluralityof coils 104 may be arranged on the top surface of wafer 102 in asymmetric array, such as a honeycomb pattern, in which sidewalls ofadjacent coils 104 are aligned with each other. In some embodiments, thehoneycomb patterns of coils 104 may cover over 91% of the surface ofwafer 102. In some embodiments, conductive element 106 of each coil isformed a minimum distance from conductive element 106 of an adjacentcoil. In some embodiments, the minimum distance is about 200 μm to about250 μm, such as about 220 μm.

In some embodiments, coil structure 100 may be used in connection withwireless charging. For example, coil structure 100 may generate amagnetic field which, when applied to a receiving coil structure, isconverted into electrical energy for charging a battery. In someembodiments, the use of a plurality of coils 104 in structure 100,instead of a single coil 104, may enable the magnetic field that iscreated to be focused in a desired direction, which may enable moreefficient wireless charging. In some embodiments, the use of a hexagonalcoil shape, and arranging the plurality of coils 104 in a honeycombpattern, may allow for a larger surface of the wafer 102 to be coveredwith coils 104 and may enable a larger number of coils to be disposed inwafer 102. In some embodiments, an increased number of coils 104 on thetop surface of wafer 102 may enable more efficient wireless charging.

In some embodiments, each coil 104 is a same or similar size to othercoils 104. As shown in FIG. 1, each coil 104 may have a hexagonal shapehaving six sides. The dimensions of each coil 104 may be determined inpart by a size of wafer 102. In some embodiments, the top surface ofwafer 102 may have a length of about 15 mm to about 20 mm, such as about15 mm, and a width of about 15 mm to about 20 mm, such as about 15 mm.For example, wafer 102 may be comprised in a package having a topsurface with a surface area of about 15×15 mm² to 20×20 mm². Each coil104 may have a length of about 50 μm to about 200 μm, and each coil 104may have a width of about 100 μm to about 200 μm.

As shown in FIG. 1A, conductive element 106 forms a continuousconductive line that extends along the top surface of wafer 102 andwinds into continuous, regularly spaced rings that are hexagonal inshape. Although a particular number of rings are depicted in FIG. 1A,each coil 104 may have more rings or fewer rings than the embodimentdepicted in FIG. 1A. Each coil 104 may have a same number of rings asthe other coils 104 in coil structure 100, or coil structure 100 maycomprise coils 104 that have different numbers of rings from other coils104. In some embodiments, each ring of conductive element 106 may beformed a distance R from an adjacent ring of the same conductive element106. In some embodiments, R may be about 150 μm to about 100 μm, such asabout 100 μm.

FIG. 2 illustrates a circuit diagram of an exemplary wireless chargingcircuit 200 including the coil structure 100 as shown in FIGS. 1Athrough 1B in accordance with some embodiments. In the embodimentdepicted in FIG. 2 coil structure 100 as depicted in FIGS. 1A and 1B isused as both a transmitting coil and a receiving coil. In someembodiments, coil structure 100 may be used as only a receiving coilstructure and a different coil structure may be used as a transmittingcoil structure. In some embodiments, coil structure 100 may only be usedas a transmitting coil structure and a different coil structure may beused as a receiving coil structure.

Wireless charging circuit 200 includes power-transmitting circuit 202for transmitting power, and power-receiving circuit 204 for receivingpower. Power-transmitting circuit 202 includes AC adapter 206,Microcontroller (MCU) and Bluetooth circuit 208, power-transmitting (TX)coil structure 100, and Bluetooth signal antenna 212. Power-receivingcircuit 204 includes Bluetooth signal antenna 214, power-receiving coilstructure 100, matching circuit 216, charging Integrated Circuit (IC)218, Bluetooth circuit 220, Power Management Integrated Circuit (PMIC)222, System Circuits 224, and battery 226. It is appreciated that theillustrated wireless charging circuits are examples, and all otherwireless charging circuits having different design are within the scopeof the present disclosure.

In accordance with some exemplary embodiments, AC adapter 206 providespower to power-transmitting (TX) coil structure 100. MCU and Bluetoothcircuit 208 may negotiate with Bluetooth circuit 220, for example, todetermine the power and the timing of the power transmission, Bluetoothsignals for the negotiation are sent and received through antennas 212and 214. For example, through the negotiation, wireless power may besent when the distance between power-transmitting circuit 202 andpower-receiving circuit 204 is lower than a pre-determined threshold,and/or when the stored power in battery 226 is lower than apre-determined threshold level.

When it is determined that power should be transmitted,power-transmitting circuit 202 starts transmitting power, which may bein the form of magnetic field at a high frequency, for example, at about6.78 MHz. The power is transmitted through transmitting coil structure100. Receiving coil structure 100 receives the power, and feeds therespective currents to charging IC 218, which includes an AC-DCconverter. PMIC 222 may have the function of DC to DC conversion,battery charging, linear regulation, power sequencing and othermiscellaneous system power functions. System circuits 224 handle logicfunctions. The converted power is charged to battery 226.

Referring to FIG. 3, a cross sectional diagram of a coil 104 isdepicted. The cross sectional view of FIG. 3 is taken along the lineA-A′ in FIG. 1. As shown in FIG. 3, coil 104 comprises conductiveelement 106 disposed in an encapsulating material 300. Encapsulatingmaterial 300 is formed of molding compounds, molding underfills,epoxies, resins, or the like.

Dielectric layer 302 is disposed over the encapsulating material 300.Dielectric layer 302 may be used as a passivation layer to isolate theunderlying metallic features from the adverse effect of moisture andother detrimental substances. Dielectric layer 302 may be formed of apolymer, which may also be a photo-sensitive material such aspolybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or the like.In some embodiments, dielectric layer 302 is formed of an inorganicmaterial(s), which may be a nitride such as silicon nitride, an oxidesuch as silicon oxide, PhosphoSilicate Glass (PSG), BoroSilicate Glass(BSG), Boron-doped PhosphoSilicate Glass (BPSG), or the like.

Dielectric layer 22 is disposed under the encapsulating material 300.Dielectric layer 22 may be used as a passivation layer to isolate theunderlying metallic features from the adverse effect of moisture andother detrimental substances. Dielectric layer 22 may also be formed ofa polymer, which may also be a photo-sensitive material such aspolybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or the like.In some embodiments, dielectric layer 22 is formed of an inorganicmaterial(s), which may be a nitride such as silicon nitride, an oxidesuch as silicon oxide, PhosphoSilicate Glass (PSG), BoroSilicate Glass(BSG), Boron-doped PhosphoSilicate Glass (BPSG), or the like. Dielectriclayer 22 may comprise a same material as dielectric layer 302, ordielectric layer 22 may comprise materials that are different fromdielectric layer 302.

Electrical connector 112 is formed at the top surface of coil 104.Electrical connector 112 connects coil 104 to an external electricalcircuit. Electrical connector 112 may be an Under-Bump Metallurgy (UBM),a metal pad, a metal pillar, or the like, and may or may not includesolder regions.

Referring to FIG. 4, another cross sectional diagram of a coil 104 isdepicted. The cross sectional view of FIG. 4 is taken along the lineB-B′ in FIG. 1. As shown in FIG. 4, coil 104 comprises conductiveelement 106 disposed in the encapsulating material 300. Along the lineB-B′, conductive element extends in a straight line and forms a sidewallof the coil 104. Dielectric layer 302 is disposed over the encapsulatinglayer 300. Electrical connector 114 is formed at the top surface of coil104. Electrical connector 114 connects coil 104 to an externalelectrical circuit. Electrical connector 114 may be an Under-BumpMetallurgy (UBM), a metal pad, a metal pillar, or the like, and may ormay not include solder regions.

FIGS. 5-13 depict intermediate steps in the formation of a coil 104 asdepicted in FIGS. 1A and 1B. FIG. 5 depicts carrier 20 and dielectriclayer 22 formed over carrier 20. Carrier 20 may be a glass carrier, aceramic carrier, or the like. Carrier 20 may have a round top-viewshape, and may have a size of a silicon wafer. There may be a releaselayer (not shown) over carrier 20, wherein the release layer may beformed of Light To Heat Conversion (LTHC) coating. The LTHC coating maybe removed along with carrier 20 from the overlying structures that willbe formed in subsequent steps.

In accordance with some embodiments of the present disclosure,dielectric layer 22 is formed over the release layer. As discussedabove, dielectric layer 22 may be used as a passivation layer to isolatethe overlying metallic features from the adverse effect of moisture andother detrimental substances. Dielectric layer 22 may be formed of apolymer, which may also be a photo-sensitive material such aspolybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or the like.In accordance with alternative embodiments of the present disclosure,dielectric layer 22 is formed of an inorganic material(s), which may bea nitride such as silicon nitride, an oxide such as silicon oxide,PhosphoSilicate Glass (PSG), BoroSilicate Glass (BSG), Boron-dopedPhosphoSilicate Glass (BPSG), or the like. Dielectric layer 22 may beformed, for example, by spin coating, lamination, Chemical VaporDeposition (CVD), or the like. In some embodiments, dielectric layer 22is a planar layer having a uniform thickness, wherein the thickness T1may be between about 5 μm and about 10 μm. The top and the bottomsurfaces of dielectric layer 22 are also planar.

Seed layer 24 is formed over dielectric layer 22, for example, throughPhysical Vapor Deposition (PVD). Seed layer 24 may be formed of copper,aluminum, titanium, or multi-layers thereof. In accordance with someembodiments of the present disclosure, seed layer 24 includes a titaniumlayer (not separately shown) and a copper layer (not separately shown)over the titanium layer. In accordance with alternative embodiments,seed layer 24 includes a single copper layer.

In some embodiments, a plurality of coils 104 is formed on carriersubstrate 20. FIGS. 6-11 depict intermediate stages in the formation ofa plurality of coils 104 on a single carrier substrate 20. FIGS. 6A, 7A,8A, 9A, 10A, 11A, 12A and 13A are cross sectional drawings that depictintermediate stages of forming a coil 104, and are taken along the lineA-A′ of FIG. 1. FIGS. 6B, 7B, 8B, 9B, 10B, 11B, 12B, 13B are also crosssectional drawings that depict intermediate stages of forming a coil104, and are taken along the line B-B′ of FIG. 1.

Referring to FIGS. 6A and 6B, photo resist 26 is formed over seed layer24, and is patterned to from openings 30. As can be seen from FIG. 6A,along the line A-A′ of FIG. 1A, a plurality of openings 30 are formed inphotoresist 26 for each coil 104. FIG. 6B shows that, along the lineB-B′ of FIG. 1A, a single opening 30 is formed in photoresist 26 foreach coil 104. In a top view of FIGS. 6A and 6B, openings 30 form aplurality of spirals, each coil 104 that is being formed correspondingto a separate spiral.

FIGS. 7A and 7B illustrate the formation of the plurality of coils 104,which includes plating a metallic material in openings 30 (FIGS. 6A and6B) and over seed layer 24. Coils 104 may include copper, aluminum,tungsten, nickel, or alloys thereof. As shown in FIG. 7A, along the lineA-A′ of FIG. 1A, in each coil 104 the conductive element 106 passesthrough the line A-A′ a plurality of times. As shown in FIG. 7B, alongthe line B-B′ of FIG. 1A, conductive element 106 is an elongated metalstructure that forms a sidewall of coil 104.

Referring to FIGS. 8A and 8B, after the plating of coils 104, photoresist 26 is removed. The portions of seed layer 24 (FIG. 5) that werepreviously covered by photo resist 26 are exposed. An etch step is thenperformed to remove the exposed portions of seed layer 24, wherein theetching may be an anisotropic or isotropic etching. The portions of seedlayer 24 that are overlapped by coil 104, on the other hand, are notetched. Throughout the description, the remaining underlying portions ofseed layer 24 are considered as being the bottom portions of coil 104.When seed layer 24 is formed of a material similar to or the same asthat of the respective overlying coil 104, seed layer 24 may be mergedwith coil 104 with no distinguishable interface between the two.Accordingly, seed layers 24 are not shown in FIGS. 8A and 8B or insubsequent drawings. In accordance with alternative embodiments of thepresent disclosure, there exist distinguishable interfaces between seedlayer 24 and the overlying plated portions of coil 104.

Next, referring to FIGS. 9A and 9B, encapsulating material 300 isencapsulated (sometimes referred to as molded) on coil 104.Encapsulating material 300 fills the gaps between neighboring portionsof coil 104. Encapsulating material 300 may include a polymer-basedmaterial, and may include a molding compound, a molding underfill, anepoxy, and/or a resin. In some embodiments, encapsulating material 300is formed on coil 104 using compression molding, transfer molding, orthe like. The encapsulating material 300 may be dispensed in liquidform. Subsequently, a curing step may be performed to cure theencapsulating material 300, wherein the curing may be a thermal curing,a UV curing, the like, or a combination thereof. In other embodiments, alamination process may be employed to form the encapsulating material300.

After being encapsulated, the top surface of encapsulating material 300is higher than the top ends of coil 104. Encapsulating material 300 mayinclude an epoxy-based material and fillers in the epoxy-based material.The fillers may be spherical particles having the same diameter ordifferent diameters. The fillers may be formed of silica (amorphousSiO₂), dry-ground micritic limestone, for example.

In a subsequent step, a planarization process such as a ChemicalMechanical Polish (CMP) process or a mechanical grinding process isperformed to reduce the top surface of encapsulating material 300, untilconductive elements 106 are exposed. Due to the planarization, the topends of conductive elements 106 are substantially level (coplanar) withthe top surfaces of encapsulating material 300. In accordance with someembodiments, after the planarization, height H1 (FIG. 9A) of conductiveelement 106 is in the range between about 50 μm and about 200 μm, andwidth W1 of conductive elements 106 is in the range between about 100 μmand about 200 μm. The ratio of width W1/H1 may be in the range betweenabout 0.5 and about 1. In accordance with some embodiments, after theplanarization, width W2 (FIG. 9B) of conductive element 106 is in therange between about 15 μm and about 20 μm.

FIGS. 10A and 10B depict the forming of a dielectric layer 302.Dielectric layer 302 may be used as a passivation layer to isolate theunderlying metallic features from the adverse effect of moisture andother detrimental substances. Dielectric layer 302 may be formed of apolymer, which may also be a photo-sensitive material such aspolybenzoxazole (PBO), polyimide, benzocyclobutene (BCB), or the like.In some embodiments, dielectric layer 302 is formed of an inorganicmaterial(s), which may be a nitride such as silicon nitride, an oxidesuch as silicon oxide, PhosphoSilicate Glass (PSG), BoroSilicate Glass(BSG), Boron-doped PhosphoSilicate Glass (BPSG), or the like. Dielectriclayer 302 may be formed, for example, by spin coating, lamination,Chemical Vapor Deposition (CVD), or the like. In some embodiments,dielectric layer 302 is a planar layer having a uniform thickness,wherein the thickness T2 may be between about 3 μm and about 10 μm. Thetop and the bottom surfaces of dielectric layer 302 are also planar.

Referring to FIGS. 11A and 11B, dielectric layer 302 is patterned toexpose the underlying conductive element 106 of each coil 104. Forexample, dielectric layer 302 may be patterned using photolithography.In some embodiments, dielectric layer 302 may be patterned by formingand patterning a photoresist layer using the same or similar processesdescribed above, and etching the sections of dielectric layer 302 thatare exposed through openings in the photoresist layer.

Next, as depicted in FIGS. 12A and 12B, electrical connectors 112 and114 are formed overlying dielectric layer 302. Electrical connectors 112and 114 electrically connect conductive element 106 to an externalelectrical circuit, such as the power-transmitting circuit 202 or powerreceiving circuit 204 of FIG. 2. In some embodiments, electricalconnectors 112 and 114 respectively comprise an under bump metallization(UBM) formed and patterned over conductive elements 106 in accordancewith some embodiments, thereby forming an electrical connection withconductive elements 106. The UBM provides an electrical connection uponwhich an electrical connector, e.g., a solder ball/bump, a conductivepillar, or the like, may be placed. In an embodiment, the UBM includes adiffusion barrier layer, a seed layer, or a combination thereof. Thediffusion barrier layer may include Ti, TiN, Ta, TaN, or combinationsthereof. The seed layer may include copper or copper alloys. However,other metals, such as nickel, palladium, silver, gold, aluminum,combinations thereof, and multi-layers thereof, may also be included. Inan embodiment, the UBM is formed using sputtering. In other embodiments,electro plating may be used.

Electrical connectors 112 and 114 may also respectively compriseconnectors over the UBM. The connectors may be solder balls, metalpillars, controlled collapse chip connection (C4) bumps, micro bumps,electroless nickel-electroless palladium-immersion gold technique(ENEPIG) formed bumps, combination thereof (e.g., a metal pillar havinga solder ball attached thereof), or the like. The connectors may includea conductive material such as solder, copper, aluminum, gold, nickel,silver, palladium, tin, the like, or a combination thereof. In someembodiments, the connectors comprise a eutectic material and maycomprise a solder bump or a solder ball, as examples. The soldermaterial may be, for example, lead-based and lead-free solders, such asPb—Sn compositions for lead-based solder; lead-free solders includingInSb; tin, silver, and copper (SAC) compositions; and other eutecticmaterials that have a common melting point and form conductive solderconnections in electrical applications. For lead-free solder, SACsolders of varying compositions may be used, such as SAC 105 (Sn 98.5%,Ag 1.0%, Cu 0.5%), SAC 305, and SAC 405, as examples. Lead-freeconnectors such as solder balls may be formed from SnCu compounds aswell, without the use of silver (Ag). Alternatively, lead-free solderconnectors may include tin and silver, Sn-Ag, without the use of copper.In some embodiments, a reflow process may be performed, giving theconnectors a shape of a partial sphere in some embodiments.Alternatively, the connectors may comprise other shapes. The connectorsmay also comprise non-spherical conductive connectors, for example.

In some embodiments, the connectors comprise metal pillars (such as acopper pillar) formed by a sputtering, printing, electro plating,electroless plating, CVD, or the like, with or without a solder materialthereon. The metal pillars may be solder free and have substantiallyvertical sidewalls or tapered sidewalls.

Referring to FIGS. 13A and 13B, the plurality of coils 104 that wereformed together on carrier substrate 20 (FIG. 5) may be singulated intoindividual coils 104, for example using a laser grooving process. Eachcoil 104 may be de-bonded from carrier substrate 20. The resultingstructures are depicted in FIG. 13A and 13B. The coils 104 may bearranged on wafer 102 in a honeycomb pattern to form coil structure 100,as depicted in FIG. 1B. Electrical connectors 112 and 114 are connectedto an external electrical circuit, such as the power transmittingcircuit 202 or the power receiving circuit 204 shown in FIG. 2. In someembodiments, the plurality of coils 104 in coil structure 100 (depictedin FIG. 1B) are formed simultaneously and configured in the honeycombpattern during formation of the coils 104.

Referring to FIG. 14, a cross sectional diagram of coil structure 100 isdepicted. In some embodiments, coil structure 100 may be used forwireless charging. In some embodiments, more efficient wireless chargingmay be achieved if the magnetic field 1400 generated by the coilstructure 100 can be focused in a particular desired direction D,instead of radiating equally in all directions from the points ofgeneration. Direction D may be a direction of a receiving coil, and thereceiving coil may be coupled to an electrical circuit that isconfigured to charge a battery. In some embodiments, the ability tofocus the magnetic field 1400 generated by coil structure 100 may beachieved by using a plurality of coils 104 in coil structure 100. Themagnetic field 1400 may be focused in a particular direction D bycontrolling an electrical current in the conductive element 106 in eachcoil 104. For example, the Ampere's circuital law provides that amagnetic field is an integrated function of an electrical current.Therefore, by controlling a frequency and amplitude of an electricalcurrent in coils 104, a phase of the magnetic field can be controlled.

In some embodiments, using a larger number of coils 104 in coilstructure 100 may lead to increased control of the magnetic field 1400that is generated by coil structure 100. In some embodiments, moreefficient wireless charging may therefore be achieved by using a largernumber of coils 104 in coil structure 100. In some embodiments, formingcoils 104 to each have a hexagonal shape, as shown in FIGS. 1A and 1B,and arranging the coils 104 in a honeycomb pattern, may enable a largernumber of coils to be formed in coil structure 100 as compared to othershapes of coils that could be used, such as a square shape. Therefore,in some embodiments, forming coils 104 to have hexagonal shapes mayenable better directional control of the magnetic field 1400 that isgenerated by coil structure 100 and may enable more efficient wirelesscharging.

In the embodiments depicted in FIGS. 1-14, each coil 104 is formed tohave a hexagonal shape. As described above, the hexagonal shape of coil104 may enable the formation of a large number of coils with a symmetricstructure, which may allow a magnetic field that is created to befocused in a desired direction by controlling electrical currents in thecoils. In some embodiments, other polygon shapes may be used. Forexample, in some embodiments coils 104 may have an octagon shape. Insome embodiments, coils 104 may have a polygon shape with n number ofsidewalls. In some embodiments, n is even integers that are greater than4.

FIG. 15 depicts a perspective view of a two different coil structures1500 and 1502. Coil structure 1500 comprises three coils 104 that havehexagonal shapes. Coil structure 1502 comprises three coils 1504 thathave square shapes. In each coil structure, it is desired to focus thegenerated magnetic field in the direction D. For coil structure 1500,direction D extends along a straight line that is perpendicular to theplane in which the coils 104 are formed, and extends from a point 1506that is equidistant to each adjacent coil 104. For coil structure 1502,direction D extends along a straight line that is perpendicular to theplane in which the coils 1504 are formed, and extends from a point 1508that is equidistant to each adjacent coil 104.

In order to control the coil structures 1500 and 1502 to respectivelyfocus a generated magnetic field in respective directions D, virtualdistances a, b, and c, and e, f, and g, are respectively calculated.Virtual distances a, b, and c are virtual straight lines that extendfrom a center point of each coil 104 to a same point that lies ondirection D of coil structure 1500. Virtual distances e, f, and g arevirtual straight lines that extend from a center point of each coil 1504to a same point that lies on direction D of coil structure 1502.Regarding coil structure 1500, due to the hexagonal shapes of coils 104,virtual distances a, b, and c are symmetrical in length. Regarding coilstructure 1502, due to the square shape of coils 1504, virtual distancese, f, and g are not symmetrical and may have different lengths. Forexample, as shown in FIG. 15, in coil structure 1502 distances e and gare equivalent in length, but distance f has a different length thandistances e and g. Due to symmetrical nature of coil structure 1500,coil structure 1500 may be more flexible in terms of the ability toadjust the electrical current in coils 104 to focus the magnetic fieldgenerated by coil structure 1500 along direction D. Due to theasymmetrical nature of coil structure 1502, coil structure 1502 may beless flexible in terms of the ability to adjust the electrical currentin coils 1504 to focus the magnetic field generated by coil structure1502 along direction D.

As described here, in some embodiments, a coil structure may be used inconnection with wireless charging. For example, a coil structure maygenerate a magnetic field which is applied to another coil structure andthen converted into electrical energy for charging a battery. In someembodiments, the use of a plurality of coils in the coil structure,instead of a single coil, may enable the magnetic field that is createdto be focused in a desired direction by controlling the electricalcurrent in the coils, which may enable more efficient wireless charging.In some embodiments, the use of a hexagonal coil shape, and arrangingthe plurality of coils in a honeycomb pattern, may enable a largernumber of coils to be used. In some embodiments, an increased number ofcoils in the coil structure may enable greater flexibility in theability to focus the magnetic field that is created in a desireddirection. Also, in some embodiments a coil structure comprisinghexagonal coils arranged in a honeycomb pattern may have increasedsymmetry, which may also enable greater flexibility in the ability tofocus the magnetic field that is created in a desired direction.

According to some embodiments, a method of forming a coil structure isprovided. The method includes forming a first conductive element on awafer, the first conductive element forming a first continuous spiralhaving a hexagonal shape in a plan view of the first conductive element.The method also includes forming a second conductive element on thewafer, the second conductive element forming a second continuous spiralhaving a hexagonal shape in a plan view of the second conductiveelement. The method also includes encapsulating the first conductiveelement and the second conductive element in an encapsulating material.The method also includes forming a dielectric layer overlying theencapsulating material. The method also includes forming a firstplurality of electrical connectors in the dielectric layer, the firstplurality of electrical connectors being electrically connected to thefirst conductive element. The method also includes forming a secondplurality of electrical connectors in the dielectric layer, the secondplurality of electrical connectors being electrically connected to thesecond conductive element.

According to some embodiments, a method is provided. The method includesforming a plurality of coils, each coil comprising a conductive elementthat forms a hexagonal shape in a plan view. The method also includesencapsulating each coil in an encapsulating material and arranging theplurality of coils on a wafer in a symmetric array.

In accordance with some embodiments, a system is provided. The systemincludes a substrate and a plurality of coils disposed over thesubstrate, each coil comprising a conductive element that forms acontinuous spiral having a hexagonal shape in a plan view of the coil.The plurality of coils is arranged on the substrate in a honeycombpattern. The system also includes a plurality of electrical connectors.Two or more of the plurality of the electrical connectors are disposedover each of the plurality of coils.

In accordance with some embodiments, a system is provided. The systemincludes a substrate and a plurality of coils over the substrate. Eachcoil includes a conductive element that forms a continuous spiral havinga hexagonal shape in a plan view of the plurality of coils. Theplurality of coils are arranged on the substrate in a honeycomb pattern.The system further includes a plurality of electrical connectors. Two ormore of the plurality of the electrical connectors are over each of theplurality of coils.

In accordance with some embodiments, a device is provided. The deviceincludes a substrate and a first coil, a second coil and a third coilover the substrate. Each of the first coil, the second coil and thethird coil includes a conductive element that forms a continuous spiralhaving a hexagonal shape in a plane parallel to a major surface of thesubstrate. The first coil, the second coil and the third coil areconfigured to generate a magnetic field in a first direction. The firstdirection extends along a first line. The first line is perpendicular tothe major surface of the substrate and extends from a point that isequidistant to each of the first coil, the second coil and the thirdcoil.

In accordance with some embodiments, a device is provided. The deviceincludes a substrate, a molding compound over the substrate, and aplurality of coils embedded into the molding compound. Each coilincludes a conductive element that forms a continuous spiral having ahexagonal shape in a plane parallel to a major surface of the substrate.The plurality of coils are arranged on the substrate in a honeycombpattern. A top surface of each coil is level with a top surface of themolding compound. The device further includes an insulating layer overthe molding compound and the plurality of coils, and a plurality ofelectrical connectors extending through the insulating layer andelectrically contacting the plurality of coils.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A system comprising: a substrate; a plurality ofcoils over the substrate, each coil comprising a conductive element thatforms a continuous spiral having a hexagonal shape in a plan view of theplurality of coils, wherein the plurality of coils are arranged on thesubstrate in a honeycomb pattern; and a plurality of electricalconnectors, wherein two or more of the plurality of the electricalconnectors are over each of the plurality of coils.
 2. The system ofclaim 1, further comprising an external electrical circuit, wherein eachof the plurality of electrical connectors is electrically coupled to theexternal electrical circuit.
 3. The system of claim 2, wherein theexternal electrical circuit is electrically coupled to a power sourceand an antenna.
 4. The system of claim 3, wherein the externalelectrical circuit further comprises a microcontroller.
 5. The system ofclaim 2, wherein the external electrical circuit is coupled to a batteryand an antenna.
 6. The system of claim 5, wherein the externalelectrical circuit further comprises a matching circuit and a bluetoothcircuit, and the plurality of electrical connectors are electricallyconnected to the matching circuit.
 7. The system of claim 1, furthercomprising an encapsulant extending along sidewalls of the plurality ofcoils.
 8. A device comprising: a substrate; and a first coil, a secondcoil and a third coil over the substrate, each of the first coil, thesecond coil and the third coil comprising a conductive element thatforms a continuous spiral having a hexagonal shape in a plane parallelto a major surface of the substrate, and wherein the first coil, thesecond coil and the third coil are configured to generate a magneticfield in a first direction, the first direction extending along a firstline, the first line being perpendicular to the major surface of thesubstrate and extending from a point that is equidistant to each of thefirst coil, the second coil and the third coil.
 9. The device of claim8, further comprising a plurality of electrical connectors, wherein twoor more of the plurality of the electrical connectors are over each ofthe first coil, the second coil and the third coil.
 10. The device ofclaim 9, further comprising a dielectric layer over and in physicalcontact with the first coil, the second coil and the third coil, whereinthe plurality of electrical connectors extend through the dielectriclayer.
 11. The device of claim 8, wherein the conductive element has afirst width and a first height, and wherein a ratio of the first widthto the first height is between about 0.5 and about
 1. 12. The device ofclaim 11, wherein the first height is between about 50 μm and about 200μm.
 13. The device of claim 12, wherein the first width is between about100 μm and about 200 μm.
 14. The device of claim 8, further comprising amolding compound encapsulating the first coil, the second coil and thethird coil.
 15. A device comprising: a substrate; a molding compoundover the substrate; a plurality of coils embedded into the moldingcompound, each coil comprising a conductive element that forms acontinuous spiral having a hexagonal shape in a plane parallel to amajor surface of the substrate, wherein the plurality of coils arearranged on the substrate in a honeycomb pattern, and wherein a topsurface of each coil is level with a top surface of the moldingcompound; an insulating layer over the molding compound and theplurality of coils; and a plurality of electrical connectors extendingthrough the insulating layer and electrically contacting the pluralityof coils.
 16. The device of claim 15, wherein each coil comprises aplurality of rings, and wherein a distance between adjacent rings isbetween about 100 μm and about 150 μm.
 17. The device of claim 16,wherein the molding compound fills a space between the adjacent rings.18. The device of claim 16, wherein the plurality of coils have a samenumber of rings.
 19. The device of claim 16, wherein different coils ofthe plurality of coils have different numbers of rings.
 20. The deviceof claim 15, wherein a bottom surface of each coil is level with abottom surface of the molding compound.